Standard radiation therapy using X-ray beams deposit their energy along the path of the beam to a target tumor. Particle therapy with protons or other ions is a type of radiotherapy that uses an external beam to provide targeted ionizing radiation to a tumor. Protons or other charged ions are sent to an accelerator to bring the particles' energy to a predetermined value. The protons or other ions then move through a beam-transport system, where magnets are used to shape, focus and/or direct the proton or other ion beam as necessary.
Traditionally, one of the key design aspects of particle therapy is the use of symmetrical tuners in a cyclotron resonator. The cavities of cyclotrons, called Dees, are tuned for matching the cavity eigenmode to the RF-Signal of the RF-Power supply system and to preserve the field balance between the cavities. Some proton therapy systems use Hill-Number Ford rotational symmetry. In addition, all cyclotron are designed to obtain Top-Bottom mirror symmetry, where the mirror plane coincides with the beam plane. A RF resonator is used to produce a voltage to accelerate particles. Within the resonator tuners are used to control the resonance frequency. The maximum accelerating voltage is expected to be in the middle of the distance between two tuners. If only one of the tuners is moved, the maximum accelerating voltage moves away from the median plane which negatively affects acceleration performance of a cyclotron.
The complexity of the cyclotron is increased greatly when both tuners need to be moved to maintain symmetry. For example, moveable sliding seals are used to separate atmospheric pressure from evacuated portions of the cyclotron. The use of a great number of moving parts increases the design complexity and the risk of failure of a moving part. Additionally, cyclotrons having symmetrical tuners require complex control software, especially when feedback loop algorithms are used for multi-dee cyclotrons. What is needed is a simplified high performance cyclotron that does not require complex control software and moving parts to reduce material, operation, and service costs of the cyclotron.